After 40 years, penicillin is still the primary therapy for gonorrhea. This proposal focuses on several aspects of the interaction of Beta-lactam antibiotics with gonococci. The areas defined for study represent a broad approach which has the potential to provide new information on several problems in the field. Studies of intrinsic resistance, which over the years led to increasing dosages of penicillin, have recently yielded new insights. In addition to an outer membrane barrier gonococci can increase penicillin resistance by modifying the affinity of their penicillin sensitive targets. Preliminary experiments have now revealed that sensitive and resistant strains respond differently, with regard to their cell wall metabolism, to inhibitory concentrations of penicillin. This raises the possibility of multiple pathways to cell death, and further studies will be conducted with the possibility of refining criteria for Beta-lactam antibiotic selection and design. A second area is concerned with increased wall hydrolysis and shedding of outer membrane vesicles upon penicillin treatment. The material which is released as membrane blebs consists of outer membrane components known to react with mammalian cells. Issues to be addressed are the mechanisms by which penicillin induces these changes and the composition of the released cell surface vesicles. The final area for study is the effect which the disruption of the cell surface of the gonococcus has on the interaction with polymorphonuclear leukocytes. In these experiments, sub-MIC concentrations of antibiotics will be employed to perturb the gonococcal cell surface. The effects of the membrane vesicles on gonococcal-PMN phagocytosis will also be assessed. These three areas delve into aspects of penicillin treatment of gonococci which are still only partially understood at best. The information obtained will strengthen the basic rationale behind Beta-lactam chemotherapy.